14. Was it because he was ill ____ he asked for leave?
A. and B. that C. that's D. so
15. Mary speaks in a low voice; ____ is difficult to know what she is saying.
A. it B. that C. so D. she
16. It was ____ I met Mr. Green in Shanghai.
A. many years that B. many years before C. many years ago that D. many years when
17. ____ is not everybody ____ can draw so well.
A. It， all B. It， that C. There， who D. There， that
18. So ____ that no fish can live in it.
A. shallow is the lake B. the lake is shallow C. shallow the lake is D. is the lake shallow